CONSTRUCTION VIBRATION IMPACTS
LE CONTE HALL SEISMIC CORRECTIONS
22 January 2002
Submitted to:
Capital Projects
University of California
1936 University Ave., 2nd Floor
Berkeley, CA 94720-1380
By:
James T. Nelson, Ph.D., P.E.
Wilson, Ihrig & Associates, Inc.
5776 Broadway
Oakland, California 94618
2
Le Conte Hall Seismic Corrections
INTRODUCTION
The University of California plans to improve the seismic integrity of Le Conte Hall on the
Berkeley Campus. The work would include moving existing researchers and experiments from
Le Conte Hall to the adjacent Le Conte Annex and Birge Hall (Surge Program), demolition of
portions of the basement and interior of Le Conte Hall, construction of foundations and interior
shear walls, installation of new mechanical equipment, and finishing the interior. Part of this
work would include removal of two columns from Le Conte Hall, including footings. The work
would occur over a two-year period, and could involve noise and vibration impacts on classroom
and research activities in the adjacent Le Conte Annex, Birge Hall, and Hildebrand Hall without
appropriate noise and vibration control provisions.
This report concerns the potential for vibration impact and mitigation options. There are two
major areas of concern. The first is the potential for construction vibration impact on sensitive
research activities in Birge Hall and possible methods for control. The second is the effect of
surging existing experiments from Le Conte Hall to Birge Hall and other locations, the new
vibration environment that these experiments will be exposed to, and the possibility of these
experiments impacting existing experiments at the new locations. The emphasis of this report is
on the former, the effect of construction vibration.
Vibration during excavation for the shear wall footings at the southern end of Le Conte Hall
would likely impact highly vibration sensitive research in the basement areas at the eastern end
of Birge Hall. The most practical mitigation involves scheduling research and heavy
construction work in such a manner that these activities do not overlap. Schedule coordination
appears to be a practical and cost-effective vibration impact mitigation approach.
The Surge Program involves relocation of certain experiments to Birge Hall, some of which are
particularly sensitive to ground vibration and structure-borne noise. Birge Hall is currently
embedded in very stiff Franciscan Formation shale, providing a low vibration response to
externally generated environmental vibration forces, such as traffic on roads, and to internally
generated building vibration. The researchers that are surged into the Birge Hall B2 level from
Le Conte Hall should benefit from a generally more favorable vibration environment than that
existing at Le Conte Hall.
In particular, Professor Zettl’s scanning tunneling microscope apparatus, currently housed in the
northern end of Le Conte Hall, would be surged to B219 Birge Hall. The vibration environment
at the basement of Birge Hall should be superior to that at the northern end of Le Conte Hall.
The apparatus Le Conte Hall is currently located in a sound deadened room. Even so, the
existing room is subject to vibration and structure-borne noise produced by door closures and
foot falls. An acoustical enclosure would be provided for Professor Zettl’s apparatus in B219
Birge Hall. The design as been reviewed, and recommendations made for increasing the
performance of this enclosure at minimal cost. The likelihood of adverse structure-borne noise
and vibration from building mechanical systems would be unlikely.
Vibration is already impacting other research work in Birge Hall. Professor Packard’s group and
Professor Davis’ group currently schedule experimental work during weekends when the
elevator and other mechanical equipment can be shut down. Professor Davis’ laboratory
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Le Conte Hall Seismic Corrections
apparatus is currently housed in a room with sound absorption applied to the walls. However,
this treatment is not sufficient prevent building noises from entering the room through the
structure. Secondly, Professor Davis’ laboratory is located closest to Le Conte Hall and the
construction work that would be conducted there, and would thus be most vulnerable to impact.
Professor Packard’s experimental apparatus is unique in that it is sensitive to any motion, and the
“noise floor” of the instrument is determined by floor vibration and structure borne noise. Their
research efforts may require lower vibration environments than currently existing today.
Professor Packard’s laboratory benefits from its location at the B2 level at the west end of Birge
Hall, furthest from the proposed construction work, and furthest from the mechanical equipment,
main ducts, and elevators.
Concerns expressed in responses to the questionnaire circulated by the Physics Department were
related to structure-borne and air-borne noise as well as structure vibration. Though the two are
closely related. That is, structure vibration produced by elevator door closures, plumbing, and
door slams can be transmitted to laboratories and radiated by laboratory walls as noise, in
addition to producing floor vibration that can be transmitted into a laboratory apparatus through
its isolators. Vibration caused by passing rubber tired vehicles on the adjacent road between
Birge Hall and Strawberry Creek did not appear to be of concern, though it may be detectable by
the most sensitive of instruments.
SURGE PROGRAM
The Surge Program involves movement of laboratory experiments and offices from Le Conte
Hall to Le Conte Annex and Birge Hall. The moves of prime interest include Professor Clark’s
laboratory, and Professor Zettl’s laboratory.
Professor Clark
Transmission of noise and vibration from Professor Clark’s new laboratory to the auditorium in
B50 is of concern. Recommendations have been provided with respect to controlling noise and
vibration produced by certain of the laboratory equipment, including elastomer isolators under
compressors, and acoustical absorption in the closet that will contain the compressors.
There should be no Le Conte Hall construction vibration impact issues related to Professor
Clark’s laboratory. His new laboratory at the west end of Birge Hall would be furthest removed
from construction work.
Professor Zettl
Professor Zettl’s laboratory includes a scanning tunneling microscope apparatus that is currently
housed in a room treated with sound absorption. The apparatus is mounted on a vibration
isolated steel honey-comb table with pneumatic isolators. The room is subject to structure borne
noise produced by door closures, specifically the main door at the north end of Le Conte Hall.
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Le Conte Hall Seismic Corrections
Professor Zettl’s laboratory would be moved to B219 Le Conte, at the bottom basement. A pit
would be provided beneath the apparatus, and the entire apparatus would be housed in a noise
reducing enclosure with heavy gauge steel walls treated with acoustical absorption.
Recommendations have been provided for increasing the separation of the enclosure from the
walls of B219 to reduce the acoustical coupling between the building walls and enclosure walls,
and for reducing structure borne noise from the concrete floor. The latter recommendation
included providing a barium loaded vinyl floor cover for the concrete floor in the enclosure.
Cutting the slab about the perimeter of the enclosure was initially recommended, but was
determined to be impractical due to ground water head. A floated concrete floor can also be
considered, but the cost of this would be high and perhaps unnecessary.
A vacuum pump serving Professor Zettl’s group would be moved to Birge Hall and housed in
one of the mechanical rooms on a vibration isolated concrete inertia base.
Other Surge Moves
The existing vacuum pumps in the mechanical room in Le Conte Hall would be moved to the 2nd
floor of Le Conte Annex. Vibration isolated inertia bases would be provided for these units to
control structure-borne noise in the lecture halls and adjoining spaces.
VIBRATION CRITERIA
Criteria have been published for vibration sensitive manufacturing and laboratory facilities,
covering relatively insensitive equipment such as bench microscopes to highly sensitive scanning
electron microscopes. These criteria are summarized in Table 1.
There are no vibration criteria available for the sensitive custom designed laboratory apparatus
used by researchers in the Physics Department. However, order-of-magnitude estimates of
vibration sensitivity are explored here for various equipment, based on the concept of a probe tip
resonance frequency and a maximum displacement of one Angstrom for the probe tip relative to
the sample. Using these assumptions, vibration sensitivity curves are developed as a function of
frequency, and can be applied to 1/3 octave or discrete frequency vibration data.
A 1/3 octave band spectrum is employed extensively for characterizing vibration, due to its
simplicity and ease of visualization. While narrow band Fourier spectra provide greater
resolution, and are useful for diagnostic purposes, they are very detailed, and may obfuscate the
significance of vibration environments. A further simplification would be to rely on a single
number descriptor, such as vibration velocity or acceleration, but such would be an over
simplification, and may result in overly conservative estimates of impact.
A schematic of a hypothetical vibration sensitive tool is provided in Figure 1. The base of the
spring-mass system represents the mounting point of the tool or probe holder, and the spring
represents the stiffness of the probe holder. The mass at the top of the spring represents the
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Le Conte Hall Seismic Corrections
probe tip. The resonance frequency of this system is given by (1/2)(K/M)1/2, where K is the
stiffness and M is the mass of the probe. The relative deflection between the probe tip and base
represents the displacement of the tip relative to the sample. The relative deflection is equal to
the spring deflection, which is a measure of the force transmitted through the spring. The force
is equal to the mass times the acceleration of the mass, and is equal to the net deflection of the
spring times the spring constant, K. Thus, for relative deflection , at frequency f0, the
acceleration of the probe tip is a0 = 42f02. Assuming that the maximum tolerable deflection is
one Angstrom = 10-10 m at frequencies much less than a probe tip resonance frequency of, for
example, 1000 Hz, the maximum base acceleration that could be tolerated would be 0.004 m/s2,
or 400 micro-g. At 1,000 Hz, the response would be limited only by damping in the system,
without which the response would be indeterminate, or infinite. Above the resonance frequency,
the relative displacement would be given by the displacement of the base, rather than its
acceleration. That is, the base would move independently of the probe tip at very high
frequencies.
A velocity representation is used for presenting and discussing vibration sensitivities. The
vibration tolerance of a tool plotted as a function of frequency appears symmetrically about its
resonance frequency when plotted in terms of velocity. The minima of the velocity tolerance
curve appear at the resonance frequencies of the tool, and are controlled by the modal damping
capacities inherent in the system. For the simple single-degree-of-freedom oscillator illustrated
in Figure 1, the maximum tolerable vibration velocity at frequencies below resonance would be
given by v0 = 2f02/f, where f is the excitation frequency. For a unit-Angstrom displacement
and resonance frequency of 1,000 Hz, the maximum vibration velocity at 100 Hz would be 6.3
/s (1  = 1e-6m). This maximum velocity would decrease by a factor of 2 for each doubling of
frequency, so that at 200 Hz, the maximum tolerable velocity would be about 3.2 /s. (In this
discussion, root-mean-square magnitudes are assumed.)
Vibration sensitivity curves are presented in Figure 2 for hypothetical probe tip resonances of
1,000 Hz, 316 Hz, and 100 Hz for a unit-Angstrom relative displacement criterion. Also shown
is the unit-Angstrom displacement curve. The intersection of the unit-Angstrom displacement
curve and the hypothetical probe tip resonance curves marks the resonance frequency of the
probe tip. Roughly speaking, the equipment would be expected to be insensitive to vibration if
the particular 1/3 octave or discrete frequency component of vibration velocity were less than
either the hypothetical probe tip resonance curve or the unit Angstrom displacement curve,
notwithstanding the effects of damping, and additional resonances.
The effect of vibration isolation systems is not represented by the curves provided in Figure 2.
The vibration tolerance of a tool would increase markedly with the introduction of vibration
isolation systems. The pneumatic isolation systems currently employed for the scanning
tunneling microscopes would be expected to raise these tolerance curves by about 10 to 20 dB,
or a factor of 3 to 10 in amplitude, at frequencies above about 5 Hz. However, the response of
the tool at its resonance frequency is controlled by damping. Lack of damping may result in
high-Q amplification of as much as 20 to 30 dB or more. Thus, the vibration isolation system
can be viewed as partial insurance against such amplification.
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Le Conte Hall Seismic Corrections
The vibration tolerance is much more complex than implied by Figure 2, but the nature of
equipment vibration tolerance curves for instruments such as semiconductor reticle inspection
machines that we have tested tend to follow the V-shape described above. Lightly damped
systems would exhibit tolerance curves that fall below those shown in Figure 2 at or near the
resonance frequency, and thus would be more susceptible to vibration than otherwise indicated.
However, the vibration isolators incorporated with these experiments would tend to compensate
for under-damped characteristics.
The vibration tolerance curves of Figure 2 may not apply to Professor Packard’s apparatus in
B241 Birge Hall. For this apparatus, any ground motion may be undesirable, as it defines a
background noise floor. Fortunately, Professor Packard’s laboratory has one of the lowest
vibration environments of any laboratory on the Berkeley Campus. Even so, experiments are
performed over weekends to avoid building vibration.
Also shown in Figure 2 is a constant velocity criterion curve of 2.5 /second (100 micro-in/sec)
used by Wilson, Ihrig & Associates as design criteria for the most sensitive of scanning electron
microscopes and similar commercial laboratory equipment. This line is slightly more
conservative than the criterion curve for Class E semiconductor manufacturing equipment, given
in Table 1, and can be considered as roughly equivalent. Achieving this criterion is almost
impossible for foot fall induced vibration of structural floors, except, perhaps, those designed
with 1 to 1.5 meter thick reinforced concrete grillages with ribs at 1.5 m spacing and columns
spaced at 5 meters. Equipment that must be sited in such an environment are usually best located
on thick grade slabs, preferably founded on rock, or supported by friction piles. The basement
floor slabs of the B2 level of Birge Hall are excellent supports.
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Le Conte Hall Seismic Corrections
Table 1 Vibration Criteria for Sensitive Equipment (Institute of Environmental Sciences,
IES-RP-CC012.1, Considerations in Clean Room Design, pg. 39)
Equipment
Residential – Daytime Occupancy
Bench Microscopes up to x100 magnification
Laboratory Robots
Class A:
Bench Microscopes up to x400
Optical balances and micro-balances
Metrology Laboratories
Inspection equipment, probes, support equipment
Class B:
Mico-surgery, eye surgery, neuro-surgery
Bench microscopes to x1000
Optical tables
Aligners, steppers for 3 micron resolution
Class C:
Electron micro-scopes up to x30,000
Micro-tomes
Magnetic Resonance Imaging systems
Aligners, steppers from 1 micron resolution
Class D:
Electron micro-scopes, transmission electron microscopes, ebeam systems operating to their limits of resolution
Mass spectrometers
Cell implant equipment
Aligners, steppers for 0.5 micron resolution
Wafer inspection systems
Class E:
Aligners, steppers for 0.25 micron resolution
Assumed to be adequate for the most demanding of sensitive
systems, including long path, laser based, small target
systems, and other systems requiring extraordinary dynamic
stability. Representative detail size is 0.1 micron
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Vibration Velocity
– micron/second 200
100
50
25
12
6
3
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Le Conte Hall Seismic Corrections
PROBE
ACCELERATION
M
BASE
ACCELERATION
K
BASE
Figure 1 Schematic of Probe Tip and Spring Support
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Le Conte Hall Seismic Corrections
1/3 OCTAVE VELOCITY LEVEL - dB RE 1 /s
40
30
31.6 /s
20
10 /s
10
3.16 /s
0
1 /s
-10
0.316 /s
-20
0.1 /s
-30
2
4
8
16
31.6
63
FREQUENCY - HZ
125
2.5 SEC
316 Hz Resonance
UNIT-ANGSTROM CURVE
100 Hz Resonance
1000 Hz Resonance
Figure 2 Vibration Sensitivity Curves
AMBIENT GROUND VERTICAL VIBRATION AT
CHEMISTRY III BUILDING IN 1986
BELOW GRADE
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250
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Le Conte Hall Seismic Corrections
MEASURED CONSTRUCTION VIBRATION
Ground vibration data were collected at several construction sites locations on the Berkeley
Campus. These sites included Hearst Mining, Latimer Hall, and Hildebrand Hall. The data were
collected with high sensitivity accelerometers and low noise preamplifiers, and recorded on
magnetic tape for later laboratory data analysis with a 1/3 octave band analyzer. All of the data
are presented as vibration velocity.
Hearst Mining Hall
The vibration data obtained at Hearst Mining were recorded at the southeast corner of the
construction area at about 18 to 45 meters from the construction equipment. The construction
equipment were operating below grade at the foundation level of the building, while the
measurements were conducted at the grade level outside of the construction zone.
Typical vibration levels observed over a measurement period of approximately 15 minutes are
compared with vibration tolerance curves in Figure 3. The data include the maximum energy
averaged vibration velocity level and the maximum vibration velocity level observed in each 1/3
octave in any one-second interval. The energy averaged velocity levels are most representative
of vibration levels occurring at the site. The levels exceed the unit-Angstrom displacement curve
by several orders of magnitude, but are comparable with the sensitivity curves of a hypothetical
tool with probe resonance frequency of 316 Hz or higher.
Data collected for a hoe ram breaking up pieces of the foundation at Hearst Mining are presented
in Figure 4. These data are representative of excavation equipment that might be used at Le
Conte Hall to chisel shale and/or break up portions of the foundation. The peak in the vibration
spectrum is at about 25 Hz, and exceeds the sensitivity curve for a 316 Hz resonance frequency
tool, but would still be acceptable for a scanning electron microscope. The data provided in
Figure 5 are similar to those provided in Figure 4, but include two hoe rams operating at the
same time. The maximum levels shown are the maximum 1/3 octave band vibration velocity
levels occurring in any one-second interval, while the energy averaged level is most
representative of typical vibration. The distance of propagation is approximately 31 meters for
both cases.
Hildebrand Hall
Vibration data were recorded at the south side of Hildebrand Hall, between Hildebrand Hall and
Strawberry Creek, during chipping operations by a small hoe ram fitted to a small track-laying
vehicle with hydraulic boom. The vehicle was located at about 5 meters below grade, and was
working on the sub-grade foundation structure of Hildebrand Hall. This source-receiver
condition is similar to that which would exist at Le Conte Hall, assuming reciprocity between
source and receiver. That is, the vibration levels observed here would be similar to those that
would be obtained if the source were at the ground surface, and the receiver were at the subgrade locations, and assuming that the input forces are the same. The data are presented in
Figure 6 for 6-meter and 15-meter horizontal distances. The data clearly exceed the vibration
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Le Conte Hall Seismic Corrections
sensitivity curves for a hypothetical tool of 316 Hz resonance frequency. At 15 meters,
representative of the source receiver distances between Le Conte Hall and B109 Birge Hall, the
vibration levels exceed the sensitivity curve for the hypothetical 316 Hz tool, but are below that
of the 1,000 Hz tool.
Latimer Hall
Vibration data were collected at the B2 level of Latimer Hall, in the hallway outside Room D23.
The main mechanical room is located at the east end of Latimer at the B1 level. The
measurement location was approximately 15 meters from the excavated trench in which a
jackhammer and tractor were used to excavate shale. Examples of the measured vibration are
presented in Figure 7. These results indicate that the vibration levels due to jack hammering and
tractor operation were indistinguishable from the background vibration that was likely produced
by the building mechanical equipment. Even so, the vibrations levels were roughly compatible
with the 2.5 micron/second criterion curve used for very sensitive scanning electron
microscopes. However, the vibration levels fell between the sensitivity curves associated with a
hypothetical instrument with probe tip resonance of 316 Hz to 1,000. The source-receiver
distance involved at this location is representative of that which would be expected between the
south end of Le Conte Hall and Birge Hall. Optical laser equipment are located in Latimer Hall
in Room D22, though no information has been obtained concerning sensitivity to vibration.
Vibration data were also collected in the stair well at the northwest corner of Lewis Hall at the
first floor level. This floor appears to be a concrete slab poured directly on grade. The data were
collected during excavation of the trench at the eastern end of Latimer Hall with a small backhoe
and large and small jackhammers. The results are presented in Figure 8 and Figure 9 for the
jackhammers and backhoe vibration, respectively. Also shown in the figures are the background
vibration levels observed between events associated with operation of these equipment. These
data indicate that the jack hammer vibration levels were significantly higher than the background
levels at frequencies above 80 Hz, exceeding the vibration sensitivity curves for a hypothetical
tool with probe tip resonance of 316 Hz, but falling below that for a probe tip resonance of 1,000
Hz. The jack hammer vibration also exceeded the design criterion of 2.5 /s for extremely
sensitive Class E laboratory instruments, though the vibration would be within criterion for
scanning electron micro-scopes, and all but the highest resolution sub micron semi-conductor
manufacturing systems, etc. The data shown for the backhoe in Figure 9 were barely above the
background, though there appeared to be some influence at the 20 and 31.6 Hz 1/3 octaves.
Finally, data for diesel crane engine generated noise and vibration are shown in Figure 10. The
crane engine appears to influence the 10 through 20 Hz 1/3 octaves, though it had little effect
relative to the vibration sensitivity curves. The vibration barely exceeded the 2.5 /s velocity
criterion. Normally, the Lewis Hall site would be considered a very acceptable location for a
highly sensitive scanning electron microscope or optical interferometer, even though the
background vibration levels exceed the sensitivity curves for hypothetical tools with probe tip
resonances of 100 and 316 Hz, and greatly exceeds the unit-Angstrom vibration displacement
curve.
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Le Conte Hall Seismic Corrections
The Lewis Hall data are particularly relevant to the Le Conte Hall / Birge Hall geometrical
arrangement. As with the Le Conte Hall machine shop, the Lewis Hall location is at a higher
elevation than the bottom of the excavation trench. The soil beneath the Lewis Hall location is,
perhaps, similar to that beneath the Le Conte Hall machine shop floor. While the source-receiver
paths are reversed, reciprocity between source and receiver makes this location analogous to the
geometrical arrangement at Le Conte Hall and Birge Hall.
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Le Conte Hall Seismic Corrections
30
-6
1/3 OCTAVE VELOCITY LEVEL - DB RE 10 M/S
40
20
10
0
-10
-20
-30
Overall
2
4
8
16
31.6
63
FREQUENCY - HZ
LEQ - CONSTRUCTION 1
MAX - CONSTRUCTION 1
LEQ - CONSTRUCTION 2
MAX - CONSTRUCTION 2
2.5 M/SEC
Figure 3
250
UNIT-ANGSTROM CURVE
1000 Hz Resonator
316 Hz Resonator
100 Hz Resonator
Typical Vibration Measured at Hearst-Mining During Various
Construction Activities
AMBIENT GROUND VERTICAL VIBRATION AT
CHEMISTRY III BUILDING IN 1986
BELOW GRADE
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125
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Le Conte Hall Seismic Corrections
30
-6
1/3 OCTAVE VELOCITY LEVEL - DB RE 10 M/S
40
20
10
0
-10
-20
-30
Overall
2
4
8
16
31.6
63
FREQUENCY - HZ
HOE RAM AT 31M - 1ST SAMPLE
HOE RAM AT 31 M - 2ND SAMPLE
2.5 M/SEC
UNIT-ANGSTROM CURVE
Figure 4
250
1000 Hz Resonator
316 Hz Resonator
100 Hz Resonator
Ground Vibration Velocity Produced by a Hoe Ram Working Against
Foundation of Hearst Mining
AMBIENT GROUND VERTICAL VIBRATION AT
CHEMISTRY III BUILDING IN 1986
BELOW GRADE
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125
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Le Conte Hall Seismic Corrections
30
-6
1/3 OCTAVE VELOCITY LEVEL - DB RE 10 M/S
40
20
10
0
-10
-20
-30
Overall
2
4
8
16
31.6
63
FREQUENCY - HZ
LEQ - 2 HOE RAMS AT 31 M
MAX - 2 HOE RAMS AT 31 M
2.5 M/SEC
UNIT-ANGSTROM CURVE
Figure 5
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125
250
1000 Hz Resonator
316 Hz Resonator
100 Hz Resonator
Ground Vibration Recorded During Operation of Two Hoe Rams at
Hearst Mining
AMBIENT GROUND VERTICAL VIBRATION AT
CHEMISTRY III BUILDING IN 1986
BELOW GRADE
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Le Conte Hall Seismic Corrections
30
-6
1/3 OCTAVE VELOCITY LEVEL - DB RE 10 M/S
40
20
10
0
-10
-20
-30
Overall
2
4
8
16
31.6
63
FREQUENCY - HZ
SMALL HOE RAM AT 6M
SMALL HOE RAM AT 15M
2.5 M/SEC
UNIT-ANGSTROM CURVE
Figure 6
125
1000 Hz Resonator
316 Hz Resonator
100 Hz Resonator
Ground Vibration Measured at the South Side of Hildebrand Hall during
Chipping of Foundation by Small Hoe Ram at 20 feet Below Grade
AMBIENT GROUND VERTICAL VIBRATION AT
CHEMISTRY III BUILDING IN 1986
BELOW GRADE
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250
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Le Conte Hall Seismic Corrections
1/3 OCTAVE VELOCITY LEVEL - DB RE 1 MICRON/SEC
30
20
10
0
-10
-20
-30
-40
OA
4
8
16
31.5
63
125
250
500
1000
FREQUENCY - Hz
Jack hammer
Tractor pushing dirt
Background
2.5 /SEC
Figure 7
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1 ANGSTROM
1000 HZ RESONATOR
316 HZ RESONATOR
100 HZ RESONATOR
Vibration Measured in Latimer at B2 Level During Rock Excavation at
Eastern End of Latimer Foundation
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Le Conte Hall Seismic Corrections
1/3 OCTAVE VELOCITY LEVEL - DB RE 1 MICRON/SEC
30
20
10
0
-10
-20
-30
-40
OA
4
8
16
31.5
63
125
250
500
1000
FREQUENCY - Hz
Sample 1 Big Jack Hammer
Sample 2 Jack Hammer
Sample 4 Small Jack Hammer
Sample 7 Jack Hammer
Background
Figure 8
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2.5 /SEC
1 ANGSTROM
1000 HZ RESONATOR
316 HZ RESONATOR
100 HZ RESONATOR
Jack Hammer Vibration In Lewis Hall from Latimer Hall Foundation
Excavation
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Le Conte Hall Seismic Corrections
1/3 OCTAVE VELOCITY LEVEL - DB RE 1 MICRON/SEC
30
20
10
0
-10
-20
-30
-40
OA
4
8
16
31.5
63
125
250
500
1000
FREQUENCY - Hz
Sample 3 Back Hoe + Tractor
Sample 5 Back hoe moving dirt
Sample 9 Back hoe engine idle
Sample 6 Background
2.5 /SEC
Figure 9
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1 ANGSTROM
1000 HZ RESONANCE
316 HZ RESONANCE
100 HZ RESONANCE
Back Hoe Generated Vibration in Lewis Hall from Latimer Hall
Foundation Excavation
20
Le Conte Hall Seismic Corrections
1/3 OCTAVE VELOCITY LEVEL - DB RE 1 MICRON/SEC
30
20
10
0
-10
-20
-30
-40
OA
4
8
16
31.5
63
125
250
500
1000
FREQUENCY - Hz
Sample 19 Crane Starts
Sample 17 Background
2.5 /SEC
1 ANGSTROM
Figure 10
2/12/16 4:18 PM
1000 HZ RESONANCE
316 HZ RESONANCE
100 HZ RESONANCE
Crane Startup Generated Vibration at Northwest Floor of Lewis Hall
from Foundation Excavation Work at Eastern End of Latimer Hall
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Le Conte Hall Seismic Corrections
AMBIENT VIBRATION AT BIRGE HALL
Ambient floor tri-axial vibration data were collected in four rooms at the B1 and B2 levels of
Birge Hall on July 20, 2001. These data were collected with seismic accelerometers adhered to
the floor with wax and were recorded on digital magnetic tape for later analysis. The rooms
included:
1
2
3
4
Room B109, Professor Davis’ scanning tunneling microscope laboratory
Room B209, a laboratory at the east end of Birge.
Room B219, Professor Zettl’s new laboratory
Room B241, Professor Packard’s SQUID detector
The floor of B109 is a reinforced concrete floor of thickness about 0.3m, supported on 1.2m high
columns of diameter 0.3m and about 1.5m on center. The remaining floors are concrete slab
floors founded directly on the rock or soil base. Based on soils data provided, the floors in B209
and B219 are likely found on the Franciscan formation shale, while the floor in Room B241 may
or may not be on the shale.
Room B109A
This room is used for research involving scanning tunneling microscopy, and would be located
closest to the proposed excavation work under Le Conte Hall. Several samples of vibration were
obtained. Figure 11 illustrates background vibration with no identifiable events, but with all
building services operating normally. The overall vibration velocity levels for the three axes are
indicated at the left hand side of the plot. The east-west component of vibration appears to be
the maximum at 125 Hz, though it is comparable with the vertical component. The 125 Hz
component is due to magneto-strictive forces produced by the 12KV transformer located in the
core of the building on the grade level. Such noise was clearly audible in the basement. The
north-south component of vibration is least in the frequency range of 31.5 to 63 Hz 1/3 octaves.
At 5 to 10 Hz 1/3 octaves, the north-south component dominates the spectrum.
Elevator operation introduced transient vibration into the room. There are two characteristic
phases of elevator operation. The first occurs when the elevator arrives at the floor, and the door
opens. The second occurs when the elevator door closes and the elevator leaves. Figure 12
illustrates the 1/3 octave band vibration velocity levels occurring during the first portion of the
elevator vibration signature. In this case, the vertical component of vibration rises above the
horizontal components at about 50 Hz and 63 Hz. The second phase of elevator operation is
represented in Figure 13. The 1/3 octave spectra are similar in both cases.
2/12/16 4:18 PM
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Le Conte Hall Seismic Corrections
1/3 OCTAVE VELOCITY LEVEL - DB RE 1 MICRON/SEC
30
20
10
0
-10
-20
-30
-40
OA
4
8
16
31.5
63
125
250
500
1000
FREQUENCY - Hz
VERTICAL
1A
E/W
1000 HZ RESONANCE
N/S
316 HZ RESONANCE
2.5 /S
100 HZ RESONANCE
MINIMUM BACKGROUND VIBRATION
Figure 11 Floor Background Vibration in B109 Birge with No Apparent Nearby Sources
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Le Conte Hall Seismic Corrections
1/3 OCTAVE VELOCITY LEVEL - DB RE 1 MICRON/SEC
30
20
10
0
-10
-20
-30
-40
OA
4
8
16
31.5
63
125
250
500
1000
FREQUENCY - Hz
VERTICAL
1 ANGSTROM
E/W
1000 HZ RESONANCE
N/S
316 HZ RESONANCE
2.5 /S
100 HZ RESONANCE
ELEVATOR 109a-6 - 1ST TRANSIENT
Figure 12 Floor Triaxial Vibration in Room 109A During Elevator Operation
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Le Conte Hall Seismic Corrections
1/3 OCTAVE VELOCITY LEVEL - DB RE 1 MICRON/SEC
30
20
10
0
-10
-20
-30
-40
OA
4
8
16
31.5
63
125
250
500
1000
FREQUENCY - Hz
VERTICAL
1 ANGSTROM
E/W
1000 HZ RESONANCE
N/S
316 HZ RESONANCE
2.5 /S
100 HZ RESONANCE
ELEVATOR 109a-7 - 2ND TRANSIENT
Figure 13 Floor Triaxial Vibration During Second Part of Elevator Operation
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Le Conte Hall Seismic Corrections
Room B207
Room B207 is located beneath Room B109, but the floor is a concrete slab founded on
presumably Franciscan Formation shale. Representative background vibration velocity levels
recorded in B207 over a period of approximately 7 minutes are plotted in Figure 14. As with
Room B109A, the east west component of vibration at the 63 Hz 1/3 octave dominates the
spectrum. Between 16 and 80 Hz, the vertical component dominates the spectrum. The overall
vibration velocity levels range from about –7 to –2 dB, less than 0.8 micron/second. The
measurement instrumentation noise floor probably dominates the spectrum below 16 Hz, though
a peak is apparent at 10 Hz.
This site is an exceptionally quiet location for conducting highly vibration sensitive research, and
would be suitable for the most sensitive semi-conductor manufacturing and inspection
equipment, or scanning electron microscopes. Without the discrete frequency component at 63
Hz, the site would be quieter still. Subsequent visits to Birge Hall suggest that the 120 Hz
discrete frequency component is due to magneto-strictive forces produced by the 12KV
transformer at the grade level core. Additional 4KV transformers are located at each floor in the
core area and additional 12KV transformers are located in the attic. These may contribute to
transformer hum at the basement level as well as other floors.
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Le Conte Hall Seismic Corrections
1/3 OCTAVE VELOCITY LEVEL - DB RE 1 MICRON/SEC
30
20
10
0
-10
-20
-30
-40
OA
4
8
16
31.5
63
125
250
500
1000
FREQUENCY - Hz
VERTICAL
1 ANGSTROM
E/W
1000 HZ RESONANCE
N/S
316 HZ RESONANCE
2.5 /S
100 HZ RESONANCE
MINIMUM BACKGROUND VIBRATION
Figure 14 Background Floor Triaxial Vibration in B207 Birge
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Le Conte Hall Seismic Corrections
B219 (Professor Zettl’s Group)
Floor vibration data collected in Room 219 are presented in Figure 15. A vacuum pump was
operating in the adjacent room B221. The 125 Hz 1/3 octave band is the most significant, the
level of which exceeds the 316 Hz resonance frequency curve for the vertical direction. Without
this component, the vibration levels would be less than the 100 Hz resonance frequency curve up
to about 125 Hz, above which there would be some excess.
Vibration recorded during elevator operation are presented in Figure 16. The 25, 31.5 and 100
Hz 1/3 octave band levels were increased substantially by the event. Even so, the 25 Hz and
31.5 Hz 1/3 octave bands were roughly comparable with the sensitivity curve for probe tips with
100 Hz resonance frequency. The effect is most noticeable in the horizontal directions, rather
than in the vertical directions. Above 250 Hz, the vertical component appears to be much less
than the horizontal components. This is a surprising result that may be due to mounting
resonance of the horizontal accelerometers.
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Le Conte Hall Seismic Corrections
1/3 OCTAVE VELOCITY LEVEL - DB RE 1 MICRON/SEC
30
20
10
0
-10
-20
-30
-40
OA
4
8
16
31.5
63
125
250
500
1000
FREQUENCY - Hz
VERTICAL
1A
EAST/WEST
1000 HZ RESONATOR
NORTH/SOUTH
316 HZ RESONATOR
2.5 /S
100 HZ RESONATOR
B219 BACKGROUND VIBRATION WITH NORMAL BUILDING SERVICES
Figure 15 Floor Vibration in Room 219 with Building Services Running Normally
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Le Conte Hall Seismic Corrections
1/3 OCTAVE VELOCITY LEVEL - DB RE 1 MICRON/SEC
30
20
10
0
-10
-20
-30
-40
OA
4
8
16
31.5
63
125
250
500
1000
FREQUENCY - Hz
VERTICAL
1 ANGSTROM
EAST/WEST
1000 HZ RESONATOR
NORTH/SOUTH
316 HZ RESONATOR
2.5 /S
100 HZ RESONATOR
B219 VIBRATION DURING ELEVATOR OPERATION
Figure 16 Floor Vibration in B219 During Elevator Operation
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Le Conte Hall Seismic Corrections
B241 Birge (Professor Packard’s Group)
Vibration data collected in Room B241 are presented in Figure 17 for normal operating
conditions of building services. These data were collected at the floor, in the northern half of the
room devoted to the experimental apparatus used by Professor Packard’s group. The vacuum
pump associated with the apparatus was not operating. The room is acoustically lined, and a
sealed sliding door was closed during the measurement. The data are comparable with the 100
Hz probe resonance curve, with modest excesses at the 63 and 125 Hz 1/3 octave bands. The
upturn at 630 Hz indicated for the horizontal directions is likely due to the mounted resonance
frequency of the horizontal accelerometers. The vibration velocity levels are roughly 20 dB
(factor of 10) less than the most stringent 2.5 /s laboratory vibration criterion curve.
A sample of vibration data collected during an unidentified event, perhaps caused by elevator
operation, is presented in Figure 18. There is little difference between these two sets of data,
except for an elevation of the 10 Hz 1/3 octave band for the North/South component. The high
frequency vibration at 630 Hz 1/3 octave also appears to be slightly elevated relative to those
shown in Figure 17.
The vibration levels observed in B241 Birge Hall are some of the lowest that have been
measured in buildings. They could be lower still if the 63 Hz and 125 Hz 1/3 octave bands were
controlled. The component at 10 Hz is unidentified. The vibration at 31.5 Hz can be related to
motors running at 1750 rpm.
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Le Conte Hall Seismic Corrections
1/3 OCTAVE VELOCITY LEVEL - DB RE 1 MICRON/SEC
30
20
10
0
-10
-20
-30
-40
OA
4
8
16
31.5
63
125
250
500
1000
FREQUENCY - Hz
VERTICAL
1 ANGSTROM
EAST/WEST
1000 HZ RESONANCE (400g)
NORTH/SOUTH
316 HZ RESONANCE (40g)
2.5 /S
100 HZ RESONANCE (g)
B241 NORMAL BUILDING SERVICES
Figure 17
2/12/16 4:18 PM
Floor Vibration in B241 Birge Hall at SQUID Detector Under Building
Service Operating Conditions
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Le Conte Hall Seismic Corrections
1/3 OCTAVE VELOCITY LEVEL - DB RE 1 MICRON/SEC
30
20
10
0
-10
-20
-30
-40
OA
4
8
16
31.5
63
125
250
500
1000
FREQUENCY - Hz
VERTICAL
1 ANGSTROM
EAST/WEST
1000 HZ RESONANCE (400g)
NORTH/SOUTH
316 HZ RESONANCE (40g)
2.5 /S
100 HZ RESONANCE (4g)
B241 ANOMALOUS EVENT
Figure 18
2/12/16 4:18 PM
Floor Vibration B241 Birge Hall during Anomalous Event
33
Le Conte Hall Seismic Corrections
SIMULATED CONSTRUCTION VIBRATION AT BIRGE HALL
Vibration data were collected in Birge Hall during testing of various mechanical equipment in
Birge Hall. During these tests, construction work was simulated in the Machine Shop in Le
Conte Hall with an Electric Jackhammer striking a steel plate. At flat hammer head was
employed. The results of these tests are compared with data collected for conditions of all
equipment on and all equipment off in Figure 19 through Figure 22 for rooms B109A, B111,
B219, and B241, respectively. These data were obtained by Fourier analyzing vibration samples
of recorded analog vibration data, converting to 1/3 octaves, and synthetically integrating the
acceleration data to velocity levels for plotting. The results are also compared with the
sensitivity curves discussed above.
The results indicate that the jack hammer vibration is very perceptible in B109a, much less so in
B111, and moderately so in B219, and very low in B241. Further, as the vibration levels decline
substantially as the jack hammer is moved to the east end of the hallway in the Machine Shop of
Le Conte Hall. However, even at the east end, the hammer vibration is well above the ambient
in B109A and to a lesser extent in B219.
The background vibration dominates the spectrum in B111, especially at 16 Hz, where a very
strong discrete frequency component is apparent. This component is not apparent in B109A,
however. The floor system in B111 is such that it may resonate at about 16 Hz, though the
amplitude is so high in B111 that floor resonance amplification does not explain the presence of
this peak. Some piece of experimental apparatus could have been causing the peak. This will be
investigated further.
The peak at the 125 Hz 1/3 octave band is also very apparent in the data collected in B109A,
B111, B219, and even B241, with or without the jack hammer. This peak is likely due to the
main 12 KV transformers. The vibration energy in B109A associated with the jackhammers far
exceeds that produced by the 12KV transformers. The same occurs in B219, though to a lesser
extent.
The 10 Hz peak observed earlier in B241 (Figure 18) at about 10 Hz is not apparent in the data
collected during the jack hammer tests (Figure 22).
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Le Conte Hall Seismic Corrections
1/3 OCTAVE VELOCITY LEVEL - DB RE 1 /SEC
30
20
10
0
-10
-20
-30
-40
OA
4
8
16
31.5
63
125
250
500
1000
FREQUENCY - Hz
JACK HAMMER AT LOC 1
JACK HAMMER AT LOC 2
JACK HAMMER AT LOC 3
ALL EQUIP ON
ALL EQUIP OFF
2.5 Micron/sec
1 ANGSTROM
1000 Hz RESONANCE (400 micro-g)
316 Hz RESONANCE ( 40 micro-g)
100 Hz RESONANCE (4 micro-g)
B109A VERTICAL VIBRATION WITH JACKHAMMER
Figure 19 Vertical Vibration in B109A with Jack Hammer in Machine Shop
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Le Conte Hall Seismic Corrections
1/3 OCTAVE VELOCITY LEVEL - DB RE 1 /SEC
30
20
10
0
-10
-20
-30
-40
OA
4
8
16
31.5
63
125
250
500
1000
FREQUENCY - Hz
JACK HAMMER AT LOC 1
JACK HAMMER AT LOC 2
JACK HAMMER AT LOC 3
ALL EQUIP ON
ALL EQUIP OFF
2.5 Micron/sec
1 ANGSTROM
1000 Hz RESONANCE (400 micro-g)
316 Hz RESONANCE ( 40 micro-g)
100 Hz RESONANCE (4 micro-g)
B111 VERTICAL VIBRATION WITH JACKHAMMER
Figure 20 Vertical Vibration in B111 with Jack Hammer in Machine Shop
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Le Conte Hall Seismic Corrections
1/3 OCTAVE VELOCITY LEVEL - DB RE 1 /SEC
30
20
10
0
-10
-20
-30
-40
OA
4
8
16
31.5
63
125
250
500
1000
FREQUENCY - Hz
JACK HAMMER AT LOC 1
JACK HAMMER AT LOC 2
JACK HAMMER AT LOC 3
ALL EQUIP ON
ALL EQUIP OFF
2.5 Micron/sec
1 ANGSTROM
1000 Hz RESONANCE (400 micro-g)
316 Hz RESONANCE ( 40 micro-g)
100 Hz RESONANCE (4 micro-g)
B219 VERTICAL VIBRATION WITH JACKHAMMER
Figure 21 Vertical Vibration in B219 with Jack Hammer in Machine Shop
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Le Conte Hall Seismic Corrections
1/3 OCTAVE VELOCITY LEVEL - DB RE 1 /SEC
30
20
10
0
-10
-20
-30
-40
OA
4
8
16
31.5
63
125
250
500
1000
FREQUENCY - Hz
JACKHAMMER AT LOC 1
JACK HAMMER AT LOC 2
JACK HAMMER AT LOC3
ALL EQUIP ON
ALL EQUIP OFF
2.5 Micron/sec
1 ANGSTROM
1000 Hz RESONANCE (400 micro-g)
316 Hz RESONANCE ( 40 micro-g)
100 Hz RESONANCE (4 micro-g)
B241 VERTICAL VIBRATION WITH JACKHAMMER
Figure 22 Vertical Vibration in B241 with Jack Hammer in Machine Shop
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Le Conte Hall Seismic Corrections
VIBRATION IMPACT MITIGATION OPTIONS
The measurement results presented above indicate that construction vibration due to hoe rams,
jack hammers, and other impulsive construction equipment vibration sources, would exceed the
background vibration velocity levels observed in B109A Birge Hall, and to a lesser extent in
B219. B241 appears to be relatively unaffected relative to background conditions by simulated
construction vibration in Le Conte, though the vibration is detectable by the measurement
instrumentation.
The jackhammer vibration would likely be detectable by the laboratory
apparatus in B241 as well. However, the electrical power was not shut down during the test, and
noise and vibration generated by transformers and various laboratory equipment were still
present. Without these sources, the vibration produced by the jack hammer in Le Conte would
likely have been more easily detected above the background in B241. Professor Packard’s group
has conducted experiments at times when building mechanical equipment were shut down, such
as the elevator, air handler, and certain pumps. This has been done on weekends when there
would be no interruption of classes and normal weekday activities.
The foregoing indicates that construction work at the south end of Le Conte Hall would cause
vibration impacts on current research activities unless mitigated. The east end of Birge Hall
would be the most affected, while the west end would be relatively unaffected, Professor
Packard’s unique detector characteristics notwithstanding.
Other sources of vibration exist near Birge Hall, such as infrequent automotive and light truck
traffic. Vibration events associated with these events were not identified, but the levels of
vibration associated with these sources may be compatible with most of the existing experiments
in Birge Hall. There was also considerable construction activity occurring at Hildebrand Hall
and Latimer, located to the east and north of Birge Hall. The vibration from Latimer and
Hildebrand Hall seismic upgrade work was not identified in the background data reported above.
The data collected at Birge Hall for simulated construction in Le Conte Hall also suggest that the
construction vibration from Latimer and Hildebrand Halls would not be observable above the
ambient.
The greatest likelihood of vibration impact on Birge Hall would be during excavation of the
footings for the shear wall and removal of foundation components at the southern end of Le
Conte Hall. The data indicate that the vibration impact on Birge Hall by construction sources at
the east side of Le Conte would be dramatically less than that caused by construction work at the
south west corner. However, there may be some residual vibration impact in B109A during
excavation at the southeast corner during removal of columns and footings. Vibration from
excavation work along the north end of Le Conte Hall would likely be undetectable in the
presence of the existing background vibration at all locations in Birge Hall, unless all electrical
and mechanical systems in Birge Hall were turned off.
Construction or demolition work at the north end of Le Conte Hall would likely not affect
experimental work in Birge Hall, except, possibly the SQUID detector in B241. Excavation
along the northern half of the north/south run of the shear wall footing would likely have little
impact on B109A. Construction work along the southern half of the north/south trench could
adversely affect the experiments in B109A.
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Le Conte Hall Seismic Corrections
The vibration control methods that may be considered include modification of construction
schedules, real time monitoring of vibration in conjunction with critical experiments, additional
vibration isolation of experimental apparatus, control of haul truck routes, and control of bob-cat
loader routes. These are discussed below.
Coordination Between Construction Work and Research
The foregoing suggests that coordination of seismic construction work at the south end of Le
Conte Hall and experimental research in Birge Hall would be necessary to avoid interfering with
experimental research. The construction phases of concern would include:
1) Earthwork, including excavation of trenches and ramp leading from basement to
Level 1
2) Hard Demolition of structural elements, including removal of columns and footings,
including installation of reinforcing bar and doweling.
3) Soft Demolition of building interior, removal of light fixtures, ceilings, etc.
4) Shot-crete shear wall construction
5) Structural steel installation
The earthwork and hard demolition activities are of greatest concern, because they would involve
jack hammers, hoe rams with spade bits, haul trucks, loaders, and other heavy equipment. Hard
demolition also includes drilling and doweling of existing concrete structures and installation of
reinforcing bar for the new shear walls.
Soft demolition includes removal of ceilings, dry-walls, plumbing, etc. Vibration from these
activities would likely be nil.
Structural steel installation was included because of the possibility of dropping large pieces of
steel during installation. Typically, preparation of I-beams and other structural elements
involves some rolling and flipping on the ground. While this activity would probably be
minimal or insignificant, the additional cost is small relative to earthwork and demolition
operations.
Shot-crete placement would involve movement of heavy ready-mix trucks, and the actual shotcrete operation may produce some modest vibration. However, it is entirely possible that the
shot-crete operation may be insignificant with respect to vibration generation. The largest source
of vibration would likely be the concrete pumper, which would likely be located on the east side
of Le Conte Hall, about midway between the north and south ends of Le Conte. While concrete
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Le Conte Hall Seismic Corrections
shot-crete installation might be a potential cause of vibration, specifically by pumping
equipment, modified scheduling of concrete deliveries could probably be conducted without a
budget impact. A day would normally be required prior to shot-crete installation to provide
formwork, check reinforcing bar, etc.
Wiring, plumbing, and finishing, would require different trades than those used for heavy
construction work. Wiring, plumbing, and finishing would not likely produce significant
vibration, and noise would be easily controlled by installation of window glazing at an early
stage. Thus, a normal work schedule can be contemplated for these trades.
Table 2 lists four construction schedule options and incremental costs, including the normal
construction schedule. These options were developed after careful consideration of the
practicality of scheduling various trades, and with a goal of providing a well defined set of
options for consideration. The costs were derived from Pankow Company’s detailed budget
estimates for hard and soft demolition, earthwork, and structural steel installation. These costs
do not include shot-creting, because this can be scheduled on a Monday through Thursday time
period without cost increment if shot-creting were found to cause impact on Birge Hall. Overall
costs for shot-creting are the largest of the construction items, so avoiding costs for shot-crete
rescheduling would be important for budget reasons. Similarly, scheduling finishing trades on a
modified schedule would result in considerable incremental cost, which might be better spent
elsewhere.
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Le Conte Hall Seismic Corrections
Table 2 Alternative Work Schedule Options & Cost Impact
Options
Work Hours
Normal
Monday thru All Levels
Friday
7am to 4pm
10 hour days Basement
Monday thru & Level 1
Thursday
(7am to 6pm
days)
Option
#1
Option
#2
Option
#3
Floors
Levels
10 hour days All Levels
Monday thru
Thursday
(7am to 6pm
days)
10 hour days All Levels
Monday thru
Thursday
(7am to 6pm
days)
Activities
Duration
(See note
2)
All activities
Additional project
cost due to premium
overtime labor (timeand-a-half)
See note 1
$0.00
18 months
Hard & soft demolition, soil
excavation & backfilling.
4 to 5
months
Hard demolition includes
concrete
jackhammering,
drilling, etc.
Hard & soft demolition, soil
excavation & backfilling.
12 to 14
months
Hard demolition includes
concrete
jackhammering,
drilling, etc.
$58,000
$115,000
18 months
All activities for
project duration
entire
$633,000
Notes:
1.
Additional labor costs are based on compensation at a rate of time-and-a-half for hours
performed in excess of an eight-hour day provided the work period does not exceed the
normal 40-hour work week. Time beyond 40 hours per week is typically paid as doubletime compensation.
2.
Project duration is currently estimated to be about 18 months starting in July of 2003.
3.
Based on estimates by Pankow per spreadsheet in email dated 1-3-02 and letter dated 1224-01.
4.
15% has been added to the totals to account for profit and overhead.
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Le Conte Hall Seismic Corrections
Modified schedules for work at just the south end of the building was initially considered. While
this would be a possibility, modified scheduling appears to be complicated, and difficult to
control. The actual construction scenario would not proceed at, say, the south end and proceed
up to the top of the building, before proceeding to the north end. Rather, the basement Level B
and Level 1 would be excavated first, followed by demolition at Level B and Level 1.
Foundations would be poured at Level B and Level 1. Level 1 would be completed before
proceeding to Level 2. Then, Level 2 would be demolished, shear walls constructed, and
completed, before proceeding to Level 3, and so forth. Further, construction work would jump
from one bay to the next bay once removed. After completion of that bay, the middle bay would
be treated. Thus, work would involve much of the floor at the same time, and not be concentrated
in any one particular area. Modified scheduling thus makes sense on a Level by level basis,
rather than on the basis of work constructed at the North or South end.
Alternative construction scheduling was discussed during meetings with the research community
at Birge Hall. The possibility of foundation excavation and demolition work proceeding 24hours per day, five days per week, until finished was not desired by the research community,
because of the need to conduct experimental work during the evening and late night hours at
various times of the week. A general consensus was obtained for conducting construction work
four days per week to allow extended duration experiments to occur Friday through Sunday, or
Thursday night through Sunday Night. Assuming that heavy construction work would cease on
Thursday at 6 pm, and resume the following Monday morning at 7 am, the time period available
for experimental work would be 85 hours, or the equivalent of about 3.5 days. The base
schedule approach of 8 hours per day for 5 days per week would allow a total of 63 hours, or
about 2.6 days, beginning Friday at 6pm.
Experiments might be conducted for more than 3.5 days. Professor Packard indicated during
informal discussion that vibration could be monitored in B241 Birge Hall during an experiment,
and experimental data collected during anomalous vibration events could be flagged for possible
contamination. Thus, such an experiment might proceed in spite of construction work, the
impact of existing building vibration notwithstanding. The experiments involving scanning
tunneling electron microscopy are evidently much less tolerant to vibration, and would have to
be restarted in the event of excessive vibration, especially when experiments are conducted in a
non-servo mode. There is also some possibility of damage to the probe tip if excessive vibration
occurs, though the amplitude of such vibration was not defined.
Additional Vibration Isolation of Laboratory Experiments
Additional vibration isolation can be provided at laboratory experiments to further isolate these
experiments from ground vibration. Active vibration isolation systems may reduce apparatus
vibration by up to 18 dB from about 1 Hz to 100 Hz and higher frequencies. However, these
isolators are very expensive, would require significant time to install, and can be subject to
maintenance problems. With these isolators, scanning tunneling microscopes might be immune
to construction vibration, as well as building mechanical equipment vibration, thus allowing
construction and experimental work to coexist. However, the construction excavation period at
the southern end of Le Conte would occupy at most about 2 months, while the excavation and
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Le Conte Hall Seismic Corrections
demolition work at both the northern and southern portions of Le Conte would require less than
four months. Two to four months might be needed to procure and install these isolators at
existing experimental apparatus, because the apparatus would have to be dismantled, the legs
shortened, and then reassembled. The cost of active vibration isolation for each apparatus could
be as high as $75,000. The long term stability of these active isolators is not known. Short term
stability can be a problem if environmental vibration exceeds the servo-controller’s range, in
which case the isolators can inject additional vibration. (However, active isolation is an effective
tool for controlling experimental apparatus vibration caused by normal building activity, and the
experimental designer may wish to consider such isolation in future laboratory set-ups,
regardless of the presence of lack of construction vibration.)
Bobcat Loader Routes
Bobcats with shovels would be used to haul material from beneath Le Conte Hall to a storage
area at the southeast corner or eastern side of Le Conte Hall. Bobcat operation should not occur
outside of Le Conte Hall west of the machine shop’s southern entrance to avoid impact on
B109A. The bobcat shovel should not be dropped unnecessarily within 75 feet of Birge Hall.
Haul Routes
Haul trucks should travel south between Le Conte and Hildebrand Hall down to Strawberry
Creek, where they would be loaded with a front-end loader, and then travel eastward along the
north side of Strawberry Creek to exit the campus at the east end. Pavement damage may be
expected. However, there has been some considerable heavy equipment operating at the south
side of Hildebrand Hall during its seismic upgrade, so that little additional impact may be
expected.
Surge Related Vibration Control of Existing Mechanical Equipment
There exist numerous mechanical equipment at the B2 level core, including two sump pumps,
and a sewage pump. While the sump pumps and sewage pump are necessarily located where
they are, they might be further isolated to reduce vibration in the B2 levels of Birge Hall, though
such isolation may prove difficult at best, or impractical. No recommendations have been made
for isolating these equipment.
A large house vacuum pump is located at the B2 level core space, and a large reciprocating
compressor for house air is located in the B1 core space. These large reciprocating machines
would be better located on vibration isolators in the attic area, removed from the B2 levels. At
the very least, they should be further vibration isolated, unless they can be turned off during
critical experiments. The existing vibration isolation appears to consist of elastomer pads that are
not be particularly effective at frequencies below perhaps 30 to 50 Hz, and certainly not at the
reciprocating frequency. Without improved isolation, they could have some impact on Professor
Zettl’s new laboratory. Their relocation or improved isolation would certainly benefit the other
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Le Conte Hall Seismic Corrections
researchers at the B2 level. The frequency of operation of these reciprocating machines was not
determined, and there is a possibility that they are no longer in use.
12 KV Transformers at Grade Level
There are three 12KV transformers located on the grade level floor, with access from the
remodeled electronics shop. These transformers produce a 120 Hz vibration component that
permeates the B1 and B2 levels, and could have some impact on Professor Zettl’s new laboratory
in B221. Vibration isolation of these transformers would benefit both Professor Zettl’s new
laboratory and other laboratories, specifically Professor Davis’ laboratory in B109A and perhaps
Professor Packard’s laboratory in B241. Vibration isolation of these transformers would likely
be difficult and costly, due to the high center of gravity of these machines. However, review of
the anchors of these transformers suggests that they may be deficient from a seismic point of
view. If seismic restraints are needed, vibration isolation might be incorporated into the design.
A structural engineer should review the seismic response of these transformers in any case.
The 12KV transformers in the attic might also be vibration isolated, but their contributions to the
B1 and B2 level vibration at 120 Hz are not known. The 4 KV transformers in the core spaces at
each of the floors do not appear to produce significant floor vibration, but this is difficult to
determine without first treating the 12KV transformers at the grade level. Additional vibration
measurements at these smaller units as well as at the 12KV transformers on in the attic might be
useful for defining their contributions.
NOISE CONTROL
Noise generated within Le Conte Hall is likely to be high at various times. The windows of the
façades of Le Conte should be sealed with plywood of minimum ¾” thickness. The perimeters
should be either taped or sealed with an acoustical caulk. The existing window glazing could be
maintained in place, with the plywood applied to the interior side. 1” duct liner should be
adhered to the plywood surface facing the glass to absorb sound and enhance the sound
transmission loss of the combined glazing and plywood.
No opening should be permitted in the western, northern, or southern façades of Le Conte Hall.
The only exception would be the entrance to the machine shop through which material would be
removed by the bobcat.
Openings in the eastern façade should kept to a minimum to control sound transmission to
Hildebrand Hall. The ceilings of the rooms in which openings are introduced should be treated
with 2” thick glass fiber duct liner to attenuate noise as it transmits through the room and
opening.
Acoustical unit absorbers should be suspended in all rooms in which work is conducted to 1)
absorb sound before it escapes to the exterior, and 2) control employee noise exposure within the
building. These absorbers can be easily moved as work on the ceilings proceeds.
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Le Conte Hall Seismic Corrections
Equipment Noise Emission Specifications
Noise emission by construction equipment should be limited by specification. Use only
equipment meeting the noise emission limits listed in Error! Reference source not found., as
measured at a distance of 50 ft from the equipment in any direction and in substantial conformity
with the provisions of the latest revisions of SAE J366b, SAE J88, and SAE J952b.
Table 3 Construction Equipment Noise Emission Limits
Type of Equipment
Noise Limit – dBA re 20 micro-Pascal
All non-stationary equipment other than 85
highway trucks; including hand tools and
heavy equipment
Highway trucks in an operating mode, 80
location, or condition
Stationary Equipment, such as generators, 70
compressors, mixers, etc.
Notes:
Measured at 15 meters from the center of the equipment, using a “slow” meter response
Limits apply to total noise emitted from equipment and associated components at all power
ranges and operating modes
Additional restrictions can be placed on noise levels at campus buildings, as described in
Table 3. Meeting these construction noise limits would require acoustical enclosures, acoustical
absorption, and high attenuation silencers. Examples of noise control provisions include:
1) Shields, impervious fences, or other physical sound barriers
2) Noise reducing enclosures
3) Effective intake and exhaust silencers on compressors and internal combustion
engines.
4) Line or cover hoppers, storage bins, and chutes with damping material
5) Restricts on use of air or gasoline driven saws
6) Situating stationary equipment to minimize noise and vibration impact, subject to
approval of UC Capital Projects
A noise and vibration specification should be made part of the construction documents. Such a
specification can be developed after review of existing specifications used at other construction
projects on campus.
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Le Conte Hall Seismic Corrections
Equipment Location
The concrete pumping machines and trucks should be located on the east side of Le Conte Hall
to avoid exposing Birge Hall and Le Conte Addition to concrete pumping noise. Stationary
equipment such as generators, compressors, batch plants, water treatment plants, should
similarly be located on the east side of Le Conte Hall to avoid impacting Birge Hall and Le
Conte Addition. Of particular concern is Hildebrand Hall, located east of Le Conte Hall.
Classroom lecture halls and offices may be adversely affected by construction noise. The
glazing of windows in these rooms should be checked and improved to provide adequate noise
reduction. Examples include laminated glass with a Sound Transmission Class rating of, for
example, STC 33. However, this may require upgrading of window mullions or sashes at
considerable expense. An alternative would be to relocate classroom instruction from the west
side of the building.
Table 3 Limits for Construction Noise at Structures
Noise Duration
Allowable Limit
Day 7am to 7pm
Continuous (lasting more than 70
two cumulative hours per day)
Intermittent (lasting less than 80
two cumulative hours per day)
Night 7pm to 7am
65
80
Construction noise control provisions should be submitted to U.C. Capital Projects for approval.
Classrooms in Gilman Hall should be identified, and any windows in classrooms facing Le
Conte Hall should be treated to control construction noise. Such treatment might include
shuttering, or installation of temporary storm windows. However, the practicality of this has not
been determined. Avoiding scheduling of classes in at the west side of Gilman might be the best
alternative, at least during heavy construction work.
CONCLUSION
The above recommendations would be expected to minimize construction noise and vibration
impacts. However, some inconvenience should be expected. The principal inconvenience could
be related to noise, rather than vibration.
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